1. Field of the Invention
This invention relates to a hammer-in expansion fastener.
2. Description of Related Art
Traditionally, expansion fasteners have been used for securing items to walls, the fastener providing a resilient lining for a bore in the wall, into which a screw is driven to secure an item to the wall. The bore has generally been pre-drilled and the fastener then pushed into it.
Expansion fasteners have been proposed which are hammered directly into the wall without the need for pre-drilling, and this can provide a more convenient means of securing an item to the wall. However, when used in plasterboard or other friable substrate such hammer-in expansion fasteners can have the effect of disintegrating the substrate at its far side, thereby reducing the depth of effective contact between the expansion fastener and the wall.
It has been proposed to provide a hammer-in expansion fastener having a tapered leading end, and such a product has reduced the extent of disintegration of the substrate. However, the taper is at a shallow angle with the result that the expansion fastener is of considerable length, and this can cause it to interfere with cables and other items beyond the far side of the wall.
According to the present invention there is provided a hammer-in expansion fastener having an elongate body which has two opposite ends, a longitudinal axis and a bore extending into it from one end to receive a screw, the other end of the body tapering inwardly to a leading end of the body to an extent allowing the hammer-in expansion fastener to be driven into a wall of building material, the said other end of the body having a non-uniform taper of (a) between 12xc2x0 to 18xc2x0 to the longitudinal axis of the body at the leading end and about 10 mm in length measured along the longitudinal axis and (b) from 4xc2x0 to 8xc2x0 to the longitudinal axis of the body at a portion remote from the leading end.
Preferably, the other end of the body is an angularly truncated tube, said truncation defining said non-uniform taper.
Preferably also, the mouth of the bore at said one end has a lateral surface extending outwardly around it to limit the extent of penetration of the hammer-in expansion fastener into the wall. The surface also provides means for spreading the load of a hammer or other driving tool when applied to the hammer-in expansion fastener.
It is further preferable for the bore to be provided with an internal partition wall which closes said bore and separates it into two distinct portions. The partition wall is made of a material (like plastic) which can be ruptured by the introduction of a screw inside the bore. The partition wall prevents disintegrated material from the wall entering the bore when the hammer-in expansion fastener is positioned into the wall. The bore may be circular in cross-section, but may advantageously be non-circular, for example oval.
Anti-rotation fins may be provided at intervals around said one end of the body projecting externally from the body so that rotation of a screw into the bore does not result in rotation of the hammer-in expansion fastener in the wall.
At least one aperture, for example slots, may be provided through the side wall of said one end of the body to allow effective radial expansion of that portion of the hammer-in expansion fastener. The at least one aperture preferably extends along the body and generally parallel to the longitudinal axis. It is also preferred that such slots extend along the body to the depth of the wall of building material.
Further according to the invention there is provided a hammer-in expansion fastener having an elongate body which has two opposite ends, a longitudinal axis and a bore extending into it from one end to receive a screw, the other end of the body having a longitudinally recessed portion which tapers inwardly in a non-uniform manner to a leading end of the body to an extent allowing the hammer-in expansion fastener to be driven into a wall of building material, the said other end being flexible to the extent that the non-uniformity of the taper of the recessed portion causes it to deflect outwardly from the longitudinal axis of the body on insertion into said wall.
Further according to the invention there is provided a hole-forming tool having an elongate body which has a longitudinal axis and that tapers inwardly to a leading end to an extent allowing it to be driven into a wall of material, the taper being (a) between 12xc2x0 and 18xc2x0 to the longitudinal axis of the body at its leading end and about 10 mm in length measured along the longitudinal axis and (b) from 4xc2x0 to 8xc2x0 to the longitudinal axis of the body at a portion remote from the leading end.
Preferably the said other end of the body is an angularly truncated tube, and said other end defines a longitudinally-extending recess which has a non-uniform taper towards the leading end. Preferably the non-uniform taper has a first portion adjacent the leading end of from 12xc2x0 to 18xc2x0, and a second portion remote from the leading end of from 4xc2x0 to 8xc2x0, measured from the longitudinal axis of the body.